Flexible electric conductor with knitted tubular covering



Patented Nov. 21, 1933 UNITED STATES PATENT OFFICE FLEXIBLE ELECTRIC CONDUCTOR WITH KNITTED TUBULAR COVERING Franz Meiwald, Vienna, Austria Serial No. 478,350

2 Claims.

This isa divisional application of Serial No. 408,961.

This invention relates to a flexible electric conductor with a knitted tubular envelope, and has 5 for its object to increase the durability of the knitted covering. The idea of covering a flexible electric conductor with a knitted envelope, which is known per se, has not been able hitherto to acquire practical importance for the reason that,

in consequence of the indispensable subsequent impregnation of the envelope, the threads of the fabric are rendered insufllciently elastic and yielding, so that when the conductor is bent the outer threads of the fabric of the covering, i. e.

those on the convex surface of the bend, become torn and broken apart.

The present invention avoids this objection by providing that the socalled stitch bars of the tubular envelope are arranged side by side and to follow a spiral curve. This arrangement of the loops prevents their becoming torn when the cord is sharply bent, since the tensile strain produced along the length of the envelope on its convex side at the bend is transferred to other portions of the outside surface of the tubular envelope,

The twisting of tubular knitted goods in the process of manufacture is already known in con-= nection with tubular cords or braids, for the pur= pose of altering the outward appearance of the same to suit certain requirements of taste. The employment of this expedient in connection with a knitted covering for electric conductors is en= tirely novel. It has required this step to render the insulation of electric conductors by means of a knitted covering practicable at all.

The manufacture of the knitted covering in accordance with the invention upon the electric conductor which forms the core can be effected 40 by means of specially constructed knitting machines, which latter form the subject of a further patent the same being Patent No. 1,814,324 issued to me on July 14, 1931.

In the accompanying drawing an electric con ductor in accordance with the invention is shown in elevation in Fig. 1, while Fig. 2 shows a knitted covering spread out fiat.

Whereas the lines of stitches or loops formed by the loops abutting end to end throughout the length of the fabric, the so-called stitch bars", lie parallel to the longitudinal axis of the tubular envelope in the case of the ordinary knitted envelope or other knitted tubular goods these lines are arranged spirally in the case of the tubular covering in accordance with the present invention. When the finished cord is sharply bent the tensile strain to which the loops on the convex side of the bend are submitted is transferred to the laterally adjacent loops which are less strained by the bending action. In the case of the impregnated protective casing for instance of electric conductors this point is of importance, since the flexibility of the threads afterhaving been hardened by impregnation is naturally slight from the start.

The obliqueness of the stitch bars, that is to say the pitch of the spiral described thereby, corresponds on an average to that of the example shown in the drawing, but can be altered within certain limits according to the diameter of the knitted tube, to the material used for the threads, to the length of the loops, etc. The length of the loops will normally increase with the diameter of the electric conductor.

I claim:-

l. The combination with a flexible electric conductor, of a knitted tubular cover therefor having its knit loops arranged side by side to form courses of loops extending spirally around the conductor, the respective loops being knit to lie spirally of the conductor and form wales extending in elongated spirals about the conductor, the spirals of the wales and courses being of the same hand.

2. ihe combination with a flexible electric conductor, of a knitted tubular cover therefor having its knit loops arranged side by side to form courses extending spirally around the conductor, the respective loops being knit to lie spirally of the conductor and form wales extending in elongated spirais about the conductor, the spirals of the courses and wales being of the same hand, said cover being impregnated with non-conducting material. 

